* TypeVariable must have a different declaration or name. The only TypeVariable that our
         * new TypeVariable _will_ be equal to is an equivalent TypeVariable that was also created
         * by us. And that equality is guaranteed to hold because it doesn't involve the JDK
         * TypeVariable implementation at all.
         */
        if (Types.NativeTypeVariableEquals.NATIVE_TYPE_VARIABLE_ONLY

     * define a separate MultimapLink interface with a separate "header" implementation, which
     * hopefully could avoid implementing Entry or ValueSetLink at all. (But note that that approach
     * requires us to define extra classes -- unfortunate under Android.) *Then* we could consider
     * lying about the fields below on the grounds that we always initialize them just after the

   */
  @SuppressWarnings("unchecked")
  public static <T extends @Nullable Object> Collector<T, ?, T> onlyElement() {
    return (Collector) ONLY_ELEMENT;
  }

  /**
   * This atrocity is here to let us report several of the elements in the stream if there were more
   * than one, not just two.
   */
  private static final class ToOptionalState {
    static final int MAX_EXTRAS = 4;

    @CheckForNull Object element;

        // didn't see it, trying to put it instead...
        Dummy sneaky = map.putIfAbsent(sample, Dummy.VALUE);
        if (sneaky == null) {
          return sample;
        } else {
          /* Someone beat us to it! Trying again...
           *
           * Technically this loop not guaranteed to terminate, so theoretically (extremely
           * unlikely) this thread might starve, but even then, there is always going to be another

    }
  }

  private static boolean equal(@Nullable Object a, @Nullable Object b) {
    return a == b || (a != null && a.equals(b));
  }

  // This one-liner saves us from some ugly casts
  protected Entry<K, V> entry(K key, V value) {
    return Helpers.mapEntry(key, value);
  }

  @Override
  protected void expectContents(Collection<Entry<K, V>> expected) {

             * corresponds to the least significant nonzero byte in lw ^ rw, since lw and rw are
             * little-endian. Long.numberOfTrailingZeros(diff) tells us the least significant
             * nonzero bit, and zeroing out the first three bits of L.nTZ gives us the shift to get
             * that least significant nonzero byte.
             */
            int n = Long.numberOfTrailingZeros(lw ^ rw) & ~0x7;

  /*
   * AbstractCollection fails the retainAll(null) test when the subject
   * collection is empty, but we'd still like to test retainAll(null) when we
   * can. We split the test into empty and non-empty cases. This allows us to
   * suppress only the former.
   */

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(ZERO)
  public void testRetainAll_nullCollectionReferenceEmptySubject() {
    try {

    }
    // Up to bufferSize, all elements of buffer are real Ts (not null unless T includes null)
    T[] topK = Arrays.copyOf(castBuffer, bufferSize);
    // we have to support null elements, so no ImmutableList for us
    return Collections.unmodifiableList(Arrays.asList(topK));
  }

        .addEqualityGroup(Collections.reverseOrder())
        .testEquals();
  }

  public void testReverseOfReverseSameAsForward() {
    // Not guaranteed by spec, but it works, and saves us from testing
    // exhaustively
    assertSame(numberOrdering, numberOrdering.reverse().reverse());
  }

  private enum StringLengthFunction implements Function<String, Integer> {
    StringLength;

        .addEqualityGroup(Collections.reverseOrder())
        .testEquals();
  }

  public void testReverseOfReverseSameAsForward() {
    // Not guaranteed by spec, but it works, and saves us from testing
    // exhaustively
    assertSame(numberOrdering, numberOrdering.reverse().reverse());
  }

  private enum StringLengthFunction implements Function<String, Integer> {
    StringLength;